1. Field of the Invention
The present invention relates to an information transmission system, an information sending device, information receiving device, an information transmission method, an information sending method, an information receiving method, and a program product using a spatial optical transmission technology.
2. Description of the Related Art
In recent years, so-called digital signage is gaining attention as an information transmission system using a spatial optical transmission technology. The digital signage refers to a system for transmitting information in a location other than home, such as outdoors, transportation facilities, storefronts and public facilities, using a display device connected to a network.
FIG. 1 is a diagram showing the use of the digital signage. In FIG. 1, an outdoor scene 100 is shown in the center, which includes pedestrians 101 and vehicles 102, as well as buildings 103 to 105 located in the background. In particular, the building 104 in the center has a large-scale display terminal 106 mounted on a wall surface thereof.
The display terminal 106 is a display device for digital signage that visualizes and displays information 107 transmitted from a server (not shown). This information 107 is, for example, information related to a certain product. In the example shown in FIG. 1, an image of a wristwatch is displayed as the product.
In order to sell this product, the price, the sales period, the sales location, etc. need to be announced.
In the example shown in FIG. 1, light modulation areas 1061 to 1064 are provided for the delivery of the above-described information. These modulation areas 1061 to 1064 are provided in portions (the four corners in FIG. 1) of the screen of the display terminal 106, and the required information is transmitted by time-serial changes of the light thereof.
As a result, when people on the street catch sight of the display on the display terminal 106 and capture an image of the advertisement using his or her mobile electronic unit 108, they can know detailed information related to the product, such as the price, the sales period and the sales location.
In the case of the example shown in FIG. 1, a picture 110 of the product and a words balloon 111 containing detailed information on the product (information on discounts, such as 50% OFF, the discount period, such as from 11:00 to 15:00, and the like) are displayed on the screen 109 of the mobile electronic unit 108.
As types of spatial “optical” transmission technology, for example, the following are known.
In U.S. Pat. No. 6,933,956, a technology for a spatial optical transmission system composed of a light transmitting unit and a light receiving unit is described.
An overview of the technology is basically as follows: A light emitting unit logically determines a bit sequence that structures information to be transmitted; alternatively selects a bit pattern sequence from two pre-prepared bit pattern sequences having a low correlation with each other, based on the determination result; modulates the light in accordance with the selection result; and transmits the modulated light. A light-receiving unit receives the light and generates a binarized signal based on the intensity of the light; generates a logic signal 1 or a logic signal 0, when the bit pattern sequence included in the binarized signal corresponds to either one of the two bit pattern sequences; and reproduces the information included in the light.
In Japanese Patent Application Laid-Open (Kokai) Publication No. 2005-267169, a technology is described which actualizes pointing by using flashing signals that are colored and have the same hue value.
In Japanese Patent Application Laid-Open (Kokai) Publication No. 2006-072778, a technology is described in which four states are transmitted and received using prescribed changes in hue difference.
In Japanese Patent Application Laid-Open (Kokai) Publication No. 2010-237820, a technology for actualizing high-speed communication is described in which, in addition to color changes, one of the colors is flashed at high speed, the light intensity is detected by a photodiode other than that of the image sensor being added, and thereby another signal is superimposed.
In Japanese Patent Application Laid-Open (Kokai) Publication No, 2009-186203, a technology is described in which transmission is performed by a combination of light-emitting bodies in three colors.
However, the technology described in U.S. Pat. No. 6,933,956 is merely a transmission technology based on the blinking of light which performs optical transmission using the logical signal 1 and the logical signal 0. Therefore, there is a problem in that, when signals (binary modulation signals) generated by binary blinking of light are received by a popularized camera having a common frame rate (about 30 fps) and information is reproduced, a considerable amount of time is required (about two seconds, described in detail hereafter).
Although modulation of multivalued light using a combination of the colors red (R), green (G), and blue (B) as in the other known technologies can be performed to solve this problem, simply performing the value multiplexing increases processing load on the light receiving device.